2711. Vrednotenje življenjske dobe lesa, zaščitenega z emulzijami voskov in bakeretanolaminskimi pripravki v tretjem razredu izpostavitveBoštjan Lesar, Miha Humar, 2010, original scientific article Abstract: V raziskavi smo preučevali življenjsko dobo lesa, izpostavljenega na prostem, v tretjem razredu izpostavitve, z dvoslojnim testom. V prvem delu raziskave smo naravnim razmeram izpostavili vzorce smrekovine, impregnirane z vodnimi emulzijami montana in polietilenskih voskov v kombinaciji z borovimi spojinami. V drugem delu testa pa smo testirali vzorce, zaščitene z baker-etanolaminskim pripravkom na vodni osnovi (Silvanolin) in posameznimi sestavinami tega pripravka. Za primerjavo smo izpostavili tudi nezaščitene vzorce smrekovine, macesnovine, bukovine in hrastovine. Skozi celotno obdobje izpostavitve smo spremljali klimatske podatke pod vzorci in na vremenski postaji. Rezultati kažejo, da impregnacija z emulzijami voskov in pripravki na osnovi bakra podaljšuje življenjsko dobo lesa, a je zaščita s pripravki na osnovi bakrovih spojin boljša. Odpornost lesa, zaščitenega z emulzijami voskov in baker etanolaminskimi pripravki, je odvisna od koncentracije emulzije/ raztopine in kakovosti lesa. Na podlagi spremljanja vlažnosti in temperature lesa smo ugotovili, da se v lesu ustvarjajo ustreznejše vlažnostne razmere za razvoj gliv, kot bi sklepali iz meritev temperature in vlažnosti zraka.
Keywords: borove spojine, bakrove spojine, les, vlažnost lesa, naravna odpornost, napovedovanje življenjske dobe
Published in DiRROS: 12.07.2017; Views: 4498; Downloads: 1925
 Full text (327,94 KB) |
2712. Osmotic component of water potential and stress adaption of adult Pedunculate oaks (Quercus robur L.) in stands with different tree densityMatjaž Čater, 2010, original scientific article Abstract: Pressure volume curves were applied to define differences in stress adaptation between two managed forest complexes and virgin forest remnant; in Murska šuma, Krakovo forest and Krakovo old growth forest. Species response between adult stands after stronger thinning and comparable stand without any silvicultural measures within same forest complex was compared in two consecutive years, 2003 and 2004. Significant differences in osmotic potential (full turgor) component for plots in Murska šuma in 2003 as well as in Krakovo forest between managed forest and old growth-forest were confirmed. In all cases, values became more negative, indicating slight capability of oaks to adapt with increasing drought stress. Reaction/stress adaptation of forests after thinning indicated well adapted mechanism to address drought stress in spite of the age. We may connect such improved drought response with increased individual space for growth and lower stand density.
Published in DiRROS: 12.07.2017; Views: 3707; Downloads: 1663
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2713. Felling maturity criteria of beech stands in SlovakiaRudolf Petráš, Julian Mecko, Aleš Kadunc, 2010, original scientific article Abstract: In this paper, we focus on the felling maturity of beech stands in Slovakia. From an economic point of view, felling maturity of stands depends on volume production, assortment composition at different stand ages, and costs of forest labour. The culmination of net value production serves as a prevailing criterion of felling maturity. Our analyses showed a modest decrease in felling costs after the stand age of 40 years. The mean value increment of beech stands was yield class dependent. The ages of stands when total mean increments culminated were, in comparison with volume production, older on average by 15 years for gross yield and by 28 years for net yield. The latter culminated between 105 and 150 years.
Published in DiRROS: 12.07.2017; Views: 4309; Downloads: 1878
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2714. Premočrtno odrezavanje kot metoda za določevanje lomnih značilnosti orientiranega lesnega tkivaMiran Merhar, Bojan Bučar, 2010, original scientific article Abstract: Prikazana je metoda določevanja kritične koncentracije napetosti na podlagi dolžine segmenta odrezka tipa I, nastalega v procesu premočrtnega ortogonalnega odrezavanja bukovine (Fagus silvatica) v smeri 90°-0°. Eksperimentalni rezi so bili narejeni na 10 mm debelih vzorcih pri cepilnem kotu 31° in 42°, debelina odrezka pa se je spreminjala v območju med 0,1 in 0,3 mm. Z metodo končnih elementov smo modelirali reprezentativni segment odrezka različnih dolžin in debelin. Spreminjali smo obremenitev segmenta ter vsakič izračunali koncentracijo napetosti na konici razpoke ter tlačno napetost v hipotetičnem odrezku. Ob predpostavki, da se razpoka pri ločevanju tkiva širi zgolj v primeru, ko je koncentracija napetosti v njenem korenu kritična, ter da se tlačne napetosti v nastajajočem odrezku nenehno povečujejo vse do mejne vrednosti, lahko na osnovi znane dolžine reprezentativnega segmenta odrezka in tlačne trdnosti vzdolž poteka tkiva izračunamo kritično koncentracijo napetosti oziroma določimo lomno togost aktualnega materiala. Razpoka napreduje namreč vse dokler tlačna napetost ne doseže porušne vrednosti, kar se zgodi na mestu loma odrezka. Kritične koncentracije napetosti, ki smo jih določili na osnovi dolžine reprezentativnega segmenta odrezka debeline 0,3 mm, se zelo dobro ujemajo z vrednostmi, dobljenimi s klasičnim frakturnim testom. Pri manjših debelinah odrezka prihaja do manjših odklonov, kar je najverjetneje posledica povečane asimetrije vzorca. Prikazano metodo lahko nedvomno označimo kot učinkovito in verodostojno, kar je tudi najbolj pomembno. Metoda je zelo enostavno in hitra, kajti lomne lastnosti aktualnega materiala je praktično moč določiti že z enim samim premočrtnim rezom. Treba je tudi poudariti, da je priprava vzorčnega materiala nezahtevna, kajti edino, na kar moramo paziti, je usmerjenost tkiva.
Keywords: premočrtno odrezovanje, odrezek, fraktura, frakturni način, koncentracija napetosti
Published in DiRROS: 12.07.2017; Views: 4240; Downloads: 1866
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2715. Optimization of energy consumption and costs of wood drying with use of different drying techniquesŽeljko Gorišek, Aleš Straže, 2010, original scientific article Abstract: The time and energy required for wood drying and therefore drying costs are among the highest in wood products manufacturing. Analysis of the drying process costs is very complex and needs to evaluate the cost of investments, energy, labour as well as defects of lumber or added value. In the present research work, we upgraded the computer aided engineering (CAE) model of wood drying processes with the economic evaluation of different drying techniques. By analyzing and comparing the costs of different drying processes, the model is able to predict the transition wood moisture content (MCt) at which the alteration from one to another drying technique would get the best results. The model was verified on data from several air- and kiln-drying experiments on 38 mm thick beech wood (Fagus sylvatica L.) boards. Computer simulation predicted advantages of combined dying beech wood with air predrying and continued and finished with kiln drying. The MCt in the winter period was at about 40% MC and decreased to 23% in favourable climate conditions in spring and summer months. The model can be also used for optimising the combination of other drying techniques.
Published in DiRROS: 12.07.2017; Views: 4292; Downloads: 1880
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2716. Padavinski režim v izbranih vrzelih in sestojih dinarskega jelovo-bukovega gozdaUrša Vilhar, 2010, original scientific article Abstract: Količina, oblika in časovna razporeditev padavin so izrednega pomena za gozdneekosisteme, saj pomembno vplivajo na preskrbo z vodo, kroženje hranil indinamiko ogljika v ekosistemu. Namen naše raziskave je bil analizirati padavinski režim v dveh sestojih in vrzelih različne velikosti v dinarskem jelovo-bukovem pragozdnem rezervatu Rajhenavski Rog ter v gospodarskem sonaravnem gozdu Snežna jama. V vegetacijskem obdobju v letih 2003 in 2004 smospremljali prepuščene padavine in odtok po deblu v vrzelih in sestojih, padavine na prostem pa v letih od 2001 do 2007. Meritve padavin v gozdni krajini so redke, čeprav so pomemben vhodni podatek za modeliranje procesov v gozdnih ekosistemih. Uporaba meritev z najbližjih meteoroloških postaj je zaradi njihove oddaljenosti vprašljiva, zato smo dnevne in mesečne količine padavin na prostem primerjali z vrednostmi za klimatološko postajo Kočevje ter EMEP-postajo Iskrba pri Kočevski Reki.
Keywords: padavine, vrzeli, gozdovi, gospdoarski gozdovi, pragozdovi, pragozdni rezervati, Kočevski Rog
Published in DiRROS: 12.07.2017; Views: 4542; Downloads: 1930
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2717. Sobivanje jelke in bukve v Dinaridih : usmeritve za ohranitveno gospodarjenje z jelkoJurij Diaci, Dušan Roženbergar, Thomas Andrew Nagel, 2010, review article Abstract: Drevesna sestava jelovo-bukovih gozdov se v prostoru in času spreminja. Nanjo vplivajo številni naravni in antropogeni dejavniki, ki delujejo neposredno ali posredno. Oblikovanje usmeritev za gojenje gozdov zato zahteva dobro poznavanje delovanja lokalnih ekoloških, zgodovinskih, gospodarskih in splošnih okoljskih dejavnikov. V prispevku prikazujemo sintezo štirih skupin raziskav, ki smo jih izpeljali v dinarskih jelovo-bukovih gozdovih v zadnjem desetletju in obravnavajo: 1) ekologijo pomlajevanja v manjših in srednjih vrzelih, 2) odziv sestojev v pragozdu Perućica na motnje srednjih jakosti (vetrolomi), 3) dolgoročne spremembe v vrstni sestavi pragozdov v jugovzhodni Evropi, in 4) odvisnost pomlajevanja v gospodarskih gozdovih od gozdnogojitvenega sistema. Namen prispevka je prikazati vlogo jelke v razvoju jelovo-bukovega gozda ter poudariti procese, ki vodijo v njeno sobivanje ali izločanje. Raziskave ekologije pomlajevanja nakazujejo, da je jelka uspešnejša na posebnih mikrorastiščih (hladnejše in vlažnejše razmere, odmrla drevesa, večja skalovitost, nižji pH tal, skromne svetlobe razmere). Na vetrolomnih površinah srednjih jakosti prevlada bukev, jelka pa se nasemeni kasneje v strnjena bukova mladovja. Naše raziskave niso potrdile hipoteze o lažjem uveljavljanju jelke v večjih sestojnih vrzelih gospodarskih gozdov. Spremembe vrstne sestave pragozdov v Sloveniji in jugovzhodni Evropi nakazujejo nazadovanje jelke v zadnjih petdesetih letih, kar je posledica več skupin vzrokov, še posebej zračnega onesnaženja in objedanja po divjadi. V Sloveniji je zmanjševanje deleža jelke v Dinaridih izrazito hitro. Primerjave z jugovzhodno Evropo kažejo, da so sicer raznovrstne strategije uveljavljanja jelke v Sloveniji neuspešne zaradi visokih gostot velikih rastlinojedih parkljarjev.
Keywords: jelka, Abies alba, bukev, Fagus sylvatica L., sobivanje, medsebojno nadomeščanje, objedanje mladja, propadanje gozdov, gojenje gozdov, Dinaridi, Dinarsko gorstvo
Published in DiRROS: 12.07.2017; Views: 4556; Downloads: 1989
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2718. Dendrochronological dating of two violins from private collections in SloveniaKatarina Čufar, Micha Beuting, Michael Grabner, 2010, original scientific article Abstract: Dendrochronological analyses were made in two violins from private collectionsin Slovenia with an aim to date the wood of their resonance boards,to assess the time of their fabrication, to define the provenance of the wood, and to establish whether the labels of the instruments were original. The origin, the history and the exact age of the instruments had previously not been known. Tree-ring measurements were done on the surface of the bellies. In violin 1, it was made of one radial board, in violin 2 of two radial boards of Norway spruce (Picea abies). In violin 1, we measured 248 tree-rings and the year of the youngest ring was 1808. The dating was confirmed with more than 20 tree-ring chronologies from Austria, Germany, and Italy. The maximal value of the cross-dating parameter t-value after Hollstein(TH) was 12.4. In violin 2, we measured 141 and 137 tree-rings on each side of the belly, and the year of the youngest ring was 1640. The dating was also obtained by cross-dating with over 20 chronologies and confirmed with statistically significant TH up to 9.2. The year of the last ring in both cases corresponded with the terminus post quem, which indicated that the belly (instrument) was fabricated after the year of formation of the youngest ring. There is no evidence about the duration of seasoning and storage of the lumber, or how many tree-rings were removed when the instrumentwas manufactured. Our dendro-provenance study showed that the violin 1 most likely originated from Austria or southern Germany. The wood for the belly of the violin 2 possibly originated from Austria and the sequence significantly matched a chronology built from the instruments made by Jacob Stainer. In both instruments, the dendrochronological dating did not confirm the inscriptions on the labels on the inside of the instrument. The presented investigation was performed in 2008 and 2009 and is to our knowledge the first dendrochronological dating of music instruments in Slovenia.
Published in DiRROS: 12.07.2017; Views: 3758; Downloads: 1687
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2720. Entrepreneurship in wood economy and a proposition for an entrepreneurial modelJože Kropivšek, Cene Šubic, Leon Oblak, 2009, original scientific article Abstract: Entrepreneurship and entrepreneurial activity of the population are of key importance for economic development, creation of new jobs and rise of the public welfare level. Some general researches (for example GEM - Global Entrepreneurship Monitor) showed that the entrepreneurial potential in Slovenia has not been completely maximized. Considering the findings from the research into entrepreneurship in wood economy we can claim the same also for the domain of wood, since we discovered numerous opportunities that are not being used at the moment. Research was made in small wood-industry companies with the help of questionnaires. On the basis of the established facts, a modern, future and development-orientated entrepreneurial model was elaborated, which is based on internal and external factors of entrepreneurship efficiency. Entrepreneurial activity is based on constant, planned and goal orientated learning and transfer (and use) of this knowledge in the business process.
Published in DiRROS: 12.07.2017; Views: 4219; Downloads: 1860
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